Long Term Evolution (LTE) wireless networks use Orthogonal Frequency Division Multiple Access (OFDMA) and Single Carrier Frequency Division Multiple Access (SC-FDMA) access schemes for the downlink (DL) and uplink (UL), respectively. User Equipments (UEs) are time and frequency multiplexed on a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH), and time and frequency synchronization between UEs guarantees optimal intra-cell orthogonality. An important UL reference signal, the Sounding Reference Signal (SRS) is defined in support of frequency dependent scheduling, link adaptation, power control and UL synchronization maintenance, which are functions handled above the Physical Layer, mainly at layer 2. The foregoing functions need, among others, a signal to noise ratio (SNR) measurement which may be derived from the SRS. Indeed, SRS processing occurring at the Physical Layer is able to deliver to upper layers mainly three metrics estimated from the SRS: channel estimates (e.g. for Downlink Beamforming) and gains across the system bandwidth (e.g. for frequency selective scheduling), noise variance and timing offset (e.g. for Timing Advance control). SNR can be directly derived from the first two above metrics or can use additional interference estimates from other reference signals such as the Demodulation Reference Signal (DMRS). A SINR estimate is described in Document (1) US 20120182857 A1 “Sounding Reference Signal Processing for LTE”, Pierre Bertrand; Anthony Ekpenyong.
However, the SNR method of document (1) determines the averaged received power of a UE from the channel estimates which are obtained in the frequency domain following Digital Fourier Transforms (DFT) processing. This situation is problematic where a plurality of SNR need be determined for associated plurality of UE's sounding signals. In fact, in that case, the method of document (1) needs one DFT processing per UE per receiving antenna. The foregoing requires a lot of processing power, memory footprint and bus load.
Therefore, it would be desirable to have a solution that would be able to calculate a SNR for a plurality of UE's sounding signals without having to use the last stage DFT processing which is proportional to the number of UEs.